1. Field of the Invention
This invention generally relates to methods and systems for generating a defect sample for a wafer.
2. Description of the Related Art
The following description and examples are not admitted to be prior art by virtue of their inclusion in this section.
One of the most important tasks during setup of wafer inspection recipes is to identify as many defect types as can be detected on a wafer. As automated recipe setup and tuning becomes more important, the need to automatically identify a good set of defects for this optimization becomes increasingly important as well. Without a good training set, automated optimization cannot function well. In addition, during manufacturing ramp up, when high and unknown defectivity is an issue, it is equally important to identify all defects on a wafer. In this situation, the interest is primarily in killer defects.
The need for developing effective sampling algorithms that achieve maximum defect type diversity has been growing with the increasing challenges in optical inspections. As the sizes of defects of interest (DOIs) shrink, optical inspections struggle to maintain differential sensitivity to these defects. To achieve the desired sensitivity, inspections tend to rely less on sophisticated defect detection algorithms and more on complex nuisance filters that leverage the wealth of defect properties (or attributes). However, tuning such filters requires a defect population that is representative of all defect types.
Examples of some methods that are currently used to sample defects from a population are described in U.S. Pat. No. 6,265,232 issued Jul. 24, 2001 to Simmons, U.S. Pat. No. 6,613,590 issued Sep. 2, 2003 to Simmons, U.S. Pat. No. 6,792,367 issued Sep. 14, 2004 to Hosoya et al., U.S. Pat. No. 6,890,775 issued May 10, 2005 to Simmons, and U.S. Pat. No. 7,912,276 issued on Mar. 22, 2011 to Shibuya et al. and U.S. Patent Application Publication Nos. 2005/0158887 published Jul. 21, 2005 to Simmons and 2008/0295048 published on Nov. 27, 2008 to Nehmadi et al., all of which are incorporated by reference as if fully set forth herein.
Accordingly, it would be advantageous to develop systems and/or methods for generating a defect sample for a wafer that can be used for one or more applications described above.